The various statements we meet with about the invention of the sphere may be equally well interpreted of its introduction only into Greece. Such, for instance, as that Eudoxus first constructed it in the thirteenth or fourteenth century B.C., or that by Clement of Alexandria, that Chiron was the originator. The oldest direct account of the names of the constellations and their component stars is that of Hesiod, who cites by name in his _Works and Days_ the Pleiades, Arcturus, Orion, and Sirius. He lived, according to Herodotus, about 884 years before Christ. The knowledge of all the constellations did not reach the Greeks at the same time, as we have seen from the omission by Homer of any mention of the Little Bear, when if he had known it, he could hardly have failed to speak of it. For in his description of the shield of Achilles, he mentions the Pleiades, the Hyades, Orion and the Bear, "which alone does not bathe in the Ocean." He could never have said this last if he had known of the Dragon and Little Bear. We may then safely conclude that the Greeks received the idea of the constellations from some older source, probably the Chaldeans. They received it doubtless as a sphere, with figured, but nameless constellations; and the Greeks by slight changes adapted them to represent the various real or imaginary heroes of their history. It would be a gracious task, for their countrymen would glory in having their great men established in the heavens. When they saw a ship represented, what more suitable than to name it the ship Argo? The Swan must be Jupiter transformed, the Lyre is that of Orpheus, the Eagle is that which carried away Ganymede, and so on. This would be no more than what other nations have done, as, for example, the Chinese, who made greater changes still, unless we consider theirs to have had an entirely independent origin. [Illustration: FIG. 9.] That the celestial sphere was a conception known to others than the Greeks is easily proved. The Arabians, for instance, certainly did not borrow it from them; yet they have the same things represented. Above is a figure of a portion of an Arabian sphere drawn in the eleventh century, where we get represented plainly enough the Great and Little Bears, the Dragon, Cassiopeia, Andromeda, Perseus, with the Triple Head of Medusa; the Triangle, one of the Fishes, Auriga, the Ram, the Bull obscurely, and the Twins.